It is well-known that an elongated coil type spring being compressed can store potential energy. Such energy as stored by the elongated coil spring cannot allow operation of a particular device requiring mechanical power over a relatively extensive period of time as the stored energy will be consumed in a non-controlled manner. In other words, the potential energy stored by the spring is not usable as premature release of such energy cannot be ensured.
Among others, a prior art publication in the technical field of the invention may be referred to as U.S. Pat. No. 4,181,299, which discloses a spring powered swing incorporating a frame supporting a swing seat for to and fro movement, a spring motor assembly within a sealed enclosure and having a male coupling head detachably engageable with a female component formed on said swing; there being a crank-controlled escapement provided with said spring motor assembly productive of incremental release of power stored in said spring. The swing seat support and the escapement crank are operatively detachably interengageable.
Therefore U.S. Pat. No. 4,181,299 discloses a spring-driven system by which periodic release of limited increments of spring energy is provided and a relatively extended operational period is obtained.
The present invention, on the other hand, is devised under the recognition that a compressible spring can be simultaneously compressed and uncompressed at opposite ends of a main shaft as provided by the characterizing features defined in claim 1.